Driving apparatus

ABSTRACT

A rotating electric machine comprises a stator having stator salient poles, three-phases windings wound around said stator salient poles, a rotor rotatable held inside the said stator, and permanent magnets inserted into said rotor and positioned opposite to said stator salient poles. The three-phase windings are concentratively wound around each of the stator salient poles, with windings of each phase wound around at more than one stator salient pole. The windings of each phase have a phase difference of voltage between at least one of the windings and the other.

BACKGROUND OF THE INVENTION

This application is a continuation application Ser. No. 10/800,752,filed Mar. 16, 2004 which is a continuation of Ser. No. 10/142,154,filed May 10, 2002 (now U.S. Pat. No. 6,734,592), which is acontinuation of Ser. No. 10/142,220, filed May 10, 2002 (now abandoned),which is a continuation of Ser. No. 09/488,637, filed Jan. 21, 2000 (nowU.S. Pat. No. 6,396,183), which is a continuation of Ser. No.08/838,745, filed Apr. 11, 1997 (now U.S. Pat. No. 6,034,460), andclaims priority of Japanese patent document JP8-091014, filed Aug. 12,1996.

FIELD OF THE INVENTION

The present invention relates generally to a permanent magnet rotatingelectric machine and an electrically driven vehicle employing same.

DESCRIPTION OF RELATED ART

Motors used in electrically driven vehicles, in particular, drivingelectric cards must ensure a sufficient running distance with a limitedbattery capacity, so that they are desired to be small, light-weight,and highly efficient.

For a motor to be small and light weight, it is required to be suitablefor high speed rotation. In this regard, permanent magnet motors areadvantageous over direct-current motors and induction motor.

Permanent magnet rotors are classified in a surface magnet rotor whichhas permanent magnets positioned along the outer periphery of the rotorand a so-called internal magnet rotor which has a permanent magnetholder within a core made of silicon steel or the like having a highermagnetic permeability than permanent magnets.

The surface magnet rotor is advantageous in ease of control, lessinfluences by reactive magnetic flux of a stator winding, low noise, andso on. However, the surface magnet rotor also has several disadvantagessuch as requirement of reinforced magnets for high speed rotation, anarrow speed control range due to difficulties in field weakeningcontrol, a low efficiency in high speed and low load operations, and soon.

The internal magnet rotor, in turn, has advantages such as thecapability of high speed rotation by field weakening control usingmagnetic pole pieces positioned along the outer periphery of magnets,the capability of highly efficient rotation in high speed and low loadoperations, utilization of reluctance torque, and so on.

Prior art internal magnet rotors are described, for example, inJP-A-5-219669, FIG. 5 of JP-A-7-39091.

Within large-size permanent magnet motors used in electric vehicles andso on, those having an internal permanent magnet rotor employ adistributed winding stator for their stator structure.

However, permanent magnet motors described in the prior art have adisadvantage that pulsating torque based on high frequency components ofpermanent magnets or auxiliary magnet poles is produced. Also, coggingtorque is produced by influence of roughness and fineness of magneticflux of stator salient poles and roughness and fineness of magnetic fluxof permanent magnets, and smooth rotation of permanent magnet motorscannot be obtained. Further, since the distributed winding stator haselongated winding ends, this causes a limitation to reduction in sizeand weight of rotating electric machines employing a distributed windingstator.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a permanent magnetrotating electric machine which has small pulsating torque and coggingtorque, and can be obtained smooth rotation thereof.

It is another object of the present invention to provide a permanentmagnet rotating electric machine having shortened winding ends, andhaving stator construction being capable to be small, light-weight.

To achieve the above object, according to a first aspect, the presentinvention provides a permanent magnet rotating electric machinecomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatably held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said windings of each phase havea phase difference of voltage between at least one of the windings andthe other.

Preferably, the permanent magnet rotating electric machine satisfiesM:P=6n:6n±2, where M is the number of the stator salient poles, P is thenumber of the permanent magnets, and n is a positive integer.

Preferably, the permanent magnet rotating electric machine satisfiesM:P=3n:3n±1, where M is the number of the stator salient poles, P is thenumber of the permanent magnets of the rotor, and n is a positiveinteger.

Preferably, in the permanent magnet rotating electric machine, thenumber of poles of the permanent magnets is eight or more.

Preferably, in the permanent magnet rotating electric machine, amagnetic pole piece area of the rotor is projected toward the stator.

Preferably, in the permanent magnet rotating electric machine, amagnetic material having a higher magnetic impermeability than thepermanent magnets is disposed between adjacent ones of the permanentmagnets.

To achieve the above object, according to a second aspect, the presentinvention provides a permanent magnet rotating electric machinecomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatable held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles.

To achieve the above object, according to an aspect, the presentinvention provides an electrically driven vehicle comprising a permanentmagnet rotating electric machine being coupled to drive wheelscomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatable held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, and control means forsupplying a voltage to said three-phase windings, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said control means suppliesvoltage which has a phase difference between at least one of thewindings and the other among each phase of three-phase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a permanent magnet rotatingelectric machine according to a first embodiment of the presentinvention, viewed from the front side thereof;

FIG. 2 is a cross-sectional view taken along the section line A-A ofFIG. 1, illustrating the permanent magnet rotating electric machineaccording to the first embodiment of the present invention;

FIG. 3 is a circuit diagram illustrating a control circuit for thepermanent magnet rotating electric machine according to the firstembodiment of the present invention;

FIGS. 4A-4C are explanatory diagrams illustrating torque generated bythe permanent magnet rotating electric machine according to the firstembodiment of the present invention;

FIGS. 5A-5C are diagrams for explaining the principles of the permanentmagnet rotating electric machine according to the first embodiment ofthe present invention;

FIG. 6 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a second embodiment of thepresent invention;

FIG. 7 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a third embodiment of the presentinvention;

FIG. 8 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a fourth embodiment of thepresent invention; and

FIG. 9 is a block diagram illustrating an electric car equipped with apermanent magnet rotating electric machine according to a fifthembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Permanent magnet rotating electric machines according to a firstembodiment of the present invention will hereinafter be described withreference to FIGS. 1-5C.

FIG. 1 is a partial cross-sectional view of a permanent magnet rotatingelectric machine according to a first embodiment of the presentinvention, viewed from the front side thereof.

Referring specifically to FIG. 1, a stator 20 of a rotating electricmachine 10 comprises a stator core 22, multi-phase stator windings 24wound around the stator core 22, and a housing 26 for securely holdingthe stator core 22 on the inner peripheral surface thereof. A rotor 30comprises a rotor core 32, permanent magnets 36 inserted into permanentmagnet inserting holes 34 formed in the rotor core 32, and a shaft 38.The shaft 38 is rotatable held by bearings 42, 44. The bearings 42, 44are supported by end brackets 46, 48, respectively, which in turn issecured to both ends of the housing 26.

A magnetic pole position detector PS for detecting the position of thepermanent magnets 36 of the rotor 30 and an encoder E for detecting theposition of the rotor 30 are disposed on a side surface of the rotor 30.The operation of the rotating electric machine 10 is controlled by acontrol unit, later described with reference to FIG. 3, in response to asignal of the magnetic pole position detector PS and an output signal ofthe encoder E.

FIG. 2 is a cross-sectional view taken along the section line A-A ofFIG. 1, wherein however, the illustration of the housing 26 is omitted.

Referring specifically to FIG. 2, the rotating electric machine 10comprises the stator 20 and the rotor 30. The rotor 20 comprises thestator core 22 and the stator windings 24. The stator core 22 comprisesan annular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, the length ofend coil portions can be reduced, and consequently the physical size ofthe rotating electric machine can also be reduced. The end coil portionsrefer to portions of the stator windings 24 projecting from the statorcore 24 to the left and right directions in FIG. 1. Since these end coilportions can be reduced, the entire rotating electric machine can bereduced in length, thus resulting in a smaller size of the rotatingelectric machine.

The U-phase of the stator windings 24 is connected to U1+, U1−, U2+,U2−, respectively; the V-phase is connected to V1+, V1−, V2+, V2−,respectively; and W-phase is connected to W1+, W1−, W2+, W2−,respectively.

The rotor 30 comprises a rotor core 32 formed of a plurality oflaminated plates made of a highly magnetically permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor core 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

The rotor core 32 is formed with the permanent magnet inserting holes 34and a hole for passing the shaft 38 therethrough, both formed by punchpress. Thus, the rotor 30 is composed of the rotor core 32 made oflaminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

The rotor core 32 may be divided in the radial direction into an inneryoke area 32A and an outer peripheral area 32B. The outer peripheralarea 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux Bφ from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to formmagnetic circuits.

The permanent magnets 36 can be accommodated in the permanent magnetinserting holes 34 which are bordered by the auxiliary magnetic polearea 32B1 in the circumferential direction and bordered by the magneticpole piece area 32B2 around the outer periphery, thus providing a motorsuitable for high speed rotation.

The concentrated winding stator is generally used in reluctance motorsand small brash-less motors. In this case, the reluctance motor includesa rotor only having auxiliary magnetic poles, while the brash-less motorhas permanent magnets directly disposed on the outer surface of a rotor.Thus, the reluctance motor generate small torque including largepulsating components.

With the surface magnetic rotor, on the other hand, it is relativelydifficult to apply a field weakening control thereto. Accordingly thesurface magnetic rotor is likely to cause a loss due to an eddy currentgenerated in surface magnets to reduce the efficiency.

In contrast, a structural combination of a rotor employing internalpermanent magnets and a concentrated winding stator allows forutilization of torque generated by flux of the permanent magnets as wellas torque generated by reluctance components of the auxiliary magneticpoles, thereby providing a higher efficiency. In addition, since thefield weakening can be achieved by the effect of the auxiliary magneticpoles, later described, an operating region can be significantlyexpanded, particularly, in a high speed region.

Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the first embodiment is free from eddy current losses.

It is assumed in the example illustrated in FIG. 2 that the rotatingelectric machine is a three-phase motor which comprises the permanentmagnet rotor 36 with the number of poles being ten, and the stator withthe number of magnetic poles being twelve. When the number of statorsalient poles is represented by M and the number of the poles of therotor magnets by P, a structure satisfying the following relationship:

M:P=6n:6n±2 (where n is a positive integer) can realize reduced torquepulsations and an increased utilization ratio of windings (windingcoefficient). It is therefore appreciated that the embodimentillustrated in FIG. 2 can provide a highly efficient, small andlight-weight rotating electric machine.

It goes without saying that while the foregoing description has beenmade in connection with an example of a motor, the first embodiment canbe similarly applied to a generator.

Next, a control unit for controlling the permanent magnet rotatingelectric machine according to the first embodiment will be describedwith reference to FIG. 3.

FIG. 3 is a circuit diagram of a control circuit for the permanentmagnet rotating electric machine according to the first embodiment.

The stator windings 24 of the rotating electric machine 24 are poweredfrom a direct current power source 80 through an invertor 82. A speedcontrol circuit (ASR) 84 calculates a speed difference

e from a speed instruction

s and an actual speed

f derived from positional information θ from the encoder E through anF/V convertor 86, and outputs a torque instruction in accordance with aPI control scheme (P represents a proportional term, and I an integralterm) or the like, i.e., a current instruction Is and a rotating angleθ1 for the rotor 30.

A phase shift circuit 88 shifts the phase of pulses from the encoder E,i.e., the positional information θ from the encoder E in accordance withthe rotating angle θ1 instructed from the speed control circuit (ASR)84. A sine wave/cosine wave generator 90 generates a sine wave output byshifting the phase of an induced voltage of each of the stator windings24 (three phases in this embodiment) based on the position detector PSfor detecting the positions of the magnetic poles of the permanentmagnets of the rotor 30 and the positional information θ on the rotor 30having its phase shifted by the phase shift circuit 88. The amount ofphase shift may be zero.

A two-phase/three-phase convertor circuit 92 outputs currentinstructions Isa, Isb, Isb to the respective phases in accordance withthe current instruction Is from the speed control circuit (ASR) 84 andan output of the sin wave/cosine wave generator 90. The respectivephases individually have current control systems (ACR) 94A, 94B, 94Cwhich control respective phase currents by providing the invertor 82with signals in accordance with the current instructions Isa, Isb, Iscand current detecting signals Ifa, Ifb, Ifc. In this event, a combinedcurrent of the respective phase currents is always formed at a positionperpendicular to the field flux or at a phase shifted position, so thatcharacteristics equivalent to those of a direct current motor can beachieved without commutator.

When the rotating electric machine of the first embodiment is applied toan electric car, the control unit has a torque control system fordirectly controlling the torque instead of the speed control circuit 84.In other words, the speed control circuit 84 is replaced with a torquecontrol circuit. The torque control circuit receives torque Ts as aninput signal, calculates torque Te from the torque Ts and actual torqueTf detected by a torque detector, and outputs a torque instruction inaccordance with a PI control scheme (P represents a proportional term,and I an integral term) or the like, i.e., a current instruction is anda rotating angle θ1 for the rotor 30.

In a permanent magnet rotating electric machine, since torque isdirectly proportional to a current, a current control system may beprovided instead of the speed control circuit 84.

The connection of the stator windings 24 is made in accordance with athree-phase stator winding scheme. More specifically, U1+, U1−, U2+, U2−are connected in the illustrated order in the U-phase; V1+, V1−, V2+,V2− are connected in the illustrated order in the V-phase; and W1+, W1−,W2+, W2− are connected in the illustrated order in the W-phase. Here,between the windings constituting the respective phases, for example,between U1+ and U2−, and between U1− and U2+ in the U-phase; between V1+and V2−, and between V1− and V2+ in the V-phase; and between W1+ andW2−, and between W1− and W2+ in the W-phase, there is a phase differenceof 30 degrees in electrical angle. Specifically explaining withreference to FIG. 2, for example, an angle θ1 between the stator salientpoles U1+ and U2− is 30 degrees, while adjacent permanent magnets 36 ofthe rotor 30 are angularly spaced by angles θ2. In this way, within thestator salient poles which are wound by the stator windings connected tothe same phase, at least one stator salient pole has a phase shiftedwith respect to the associated permanent magnet. Take, as an example, astator salient pole around which the winding U1− is wound and a statorsalient pole around which the winding U2+ is wound. Assuming that U1− isin phase with the permanent magnet 36A, U1− is shifted from thepermanent magnet 36B by an angular distance of 30 degrees. Thiscontributes to a reduction in pulsating pulse which may cause a problemin the concentrated winding stator. The reason for this reduction willbe described later with reference to FIG. 4.

A concentrated winding should be constructed such that respectivewindings do not overlap on the gap surface as illustrated in FIG. 1.This eliminates interference between the respective windings, and asmall, light-weight and simple rotating electric machine can berealized.

Also, by selecting adjacent windings to be connected to the same phaseas illustrated, the connection is facilitated. Specifically, in theU-phase, U1+ and U2− are adjacent, and U1− and U2+ are adjacent. In theV-phase, V1+ and V2− are adjacent, and V1− and V2+ are adjacent.Similarly, in the W-phase, W1+ and W2− are adjacent, and W1− and W2+ areadjacent, thus facilitating the connection of these windings.

Next, the reason for the reduction in torque pulsation will be explainedwith reference to FIGS. 4A-4C.

FIGS. 4A-4C show the torque generated by the permanent magnet rotatingelectric machine according to the first embodiment of the presentinvention.

FIG. 4A represents torque which is generated when the respective statorwindings of U1+, U1−, V1+, V1−, W1+, W1− are applied with a sine wavecurrent based on a signal from the sine wave/cosine wave generatorcircuit 90 illustrated in FIG. 3. While uniform torque would begenerated if no harmonics were included, the inclusion of harmoniccomponents caused by the permanent magnets, harmonic components due tothe auxiliary magnetic poles, and so on cause torque pulsation at aperiod of 60 degrees in electrical angle, as illustrated.

FIG. 4B represents torque which is generated when the respective statorwindings of U2+, U2−, V2+, V2−, W2+, W2− are applied with a sine wavecurrent. Since the represented torque includes harmonic componentscaused by the permanent magnets, harmonic components due to theauxiliary magnetic poles, and so on, as is the case of the torquerepresented in FIG. 4A, torque pulsations are generated at a period of60 degrees in electrical angle.

It should be noted herein that since there is a phase difference of 30degrees in electrical angle between the stator salient poles aroundwhich U1+, U1−, V1+, V1−, W1+, W1− of the stator windings 24 are woundand the stator salient poles around which U2+, U2−, V2+, V2−, W2+, W2−of the stator windings 24 are wound, the torque pulsations generatedthereby are in opposite phase to each other.

Thus, a combination of torque of FIGS. 4A and 4B exhibits reducedpulsations as shown in FIG. 4C.

Referring back to FIG. 2, in the example in which the ratio of thenumber of permanent magnet M to the number of stator salient poles P isdetermined to be 10:12, the cogging torque of the permanent magnetrotating electric machine exhibits a number of pulsations per rotationequal to the least common multiple of the number of permanent magnetsand the number of stator salient poles , i.e., 60 per rotation in thisexample. Generally, the cogging torque is smaller as the number ofpulsations per rotation is larger.

In a conventionally used motor having a general surface magnet rotor anda concentrated winding stator, the ratio of the number of permanentmagnets M to the number of stator salient poles P is typically 2:3. Thisratio corresponds to 10:15 when the number of permanent magnets M ischanged from two to ten which is the number of permanent magnets M inthe example illustrated in FIG. 2. In this case, the number ofpulsations per rotation of the cogging torque is calculated to be 30which is the least common multiple of 10 and 15. It will be understoodfrom this discussion that the structure of the first embodiment canreduce the cogging torque more than conventional motor of the same type.

In addition, pulsating torque possibly occurring when a current isconducted can be reduced by the principles shown in FIG. 4.

Next, the operation principles of the field weakening control for thepermanent magnet rotating electric machine according to the firstembodiment will be explained with reference to FIGS. 5A-5C.

Torque T generated by a permanent magnet rotating electric machine isgenerally expressed by the following equation:T={E0·Iq+(Xq−Xd)·Id·Iq}/wwhere E0 is an induced voltage; Xq is reactance on q-axis; Xd isreactance on d-axis; Id is a current on d-axis; Iq is a current onq-axis; and w is an angular rotational speed.

Referring first to FIG. 5A, a permanent magnet 36 is positioned ond-axis, and an auxiliary magnetic pole area 32B1 having a highermagnetic permeability than the permanent magnet 36 is positioned onq-axis. In this arrangement, respective vectors are represented in FIG.5A. A current Im, which is a combination of the d-axis current Id andthe q-axis current Iq, is controlled in the illustrated direction by thecurrent instructions Isa, Isb, Isc generated by the control circuitillustrated in FIG. 3, calculations of output positions of the magneticpole position detector PS and the encoder E of the rotating electricmachine, and so on.

In the foregoing equation, the first term expresses a component oftorque generated by the permanent magnet, and the second term expressesa reluctance component generated by the auxiliary magnetic pole area32B1.

A rotating electric machine for electric car must be controlled so as tomaximize the torque/current particularly during a low speed operation.FIG. 5A shows a vector diagram when the rotating electric machine iscontrolled to generate a maximum torque/current. In this event, therotating electric machine is controlled to apply an increasedmagnetomotive force to the auxiliary magnetic pole 32B1, thus takingadvantage of the torque generated by the permanent magnet, expressed bythe first term, as well as the reluctance torque generated by theauxiliary magnetic pole 32B1, expressed by the second term.

In a high speed region, on the other hand, the torque may be small.Rather, the Id component is increased to cancel the induced voltage E0of the permanent magnet by Xd·Id in order to weaken the flux of thepermanent magnet 36, whereby the rotating electric machine can berotated up to a high speed region. FIG. 5B shows a vector diagram duringa high speed operation.

The currents Id, Iq are controlled by the phase shift circuit 88 of thecontrol circuit illustrated in FIG. 3.

Referring next to FIG. 5C, a broken line T2 represents torque generatedby a conventional surface magnet rotating electric machine. It can beseen from the broken line T2 that the torque is decreased in a highspeed region. A solid line T1, in turn, represents the relationshipbetween the torque and the speed of the permanent magnet rotatingelectric machine according to the first embodiment, provided by thecontrol described above. Since the current can more easily pass throughas compared with the conventional surface magnet rotating electricmachine, the permanent magnet rotating electric machine of the firstembodiment can be operated in a higher speed region.

According to the first embodiment, since a concentrated winding statoris employed, the end coil portions of the stator can be reduced, so thata smaller rotating electric machine can be provided.

Also, since the stator salient poles, having wound therearound thestator windings connected to the same phase, include at least onesalient pole which has a different phase with respect to the associatedpermanent magnet, this configuration reduces the pulsating torque whichmay cause a problem in the concentrated winding stator.

Further, since the permanent magnet rotor is provided with auxiliarymagnetic poles, a structure suitable for field weakening control isrealized, thereby providing a rotating electric machine appropriate tohigh speed rotation.

Furthermore, since an auxiliary magnetic pole area made of a magneticmaterial having a higher magnetic permeability than the permanentmagnets is positioned between the permanent magnets, increased torquecan be generated.

Moreover, the permanent magnets are surrounded by silicon steel plates,so that a structure suitable for high speed rotation can be provided.

Next, a permanent magnet rotating electric machine according to anotherembodiment of the present invention will be described with reference toFIG. 6.

FIG. 6 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to a second embodiment of thepresent invention.

The second embodiment is characterized by a three-phase motor structurewhich comprises a permanent magnet rotor 36 having ten poles (P=10) anda stator having nine magnetic poles (M=9). Thus, when the ratio of thenumber of stator salient poles M to the number of magnetic poles of thestator magnet P (M:P) is 3n:3n±1, reduced torque pulsations and anincreased utilization ratio of windings (winding coefficient) can berealized, so that a highly efficient, small, and light-weight rotatingelectric machine can be provided.

Referring specifically to FIG. 6, the rotating electric machine 10comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, the length ofend coil portions can be reduced, and consequently the physical size ofthe rotating electric machine can also be reduced.

The U-phase of the stator windings 24 is connected to U1+, U1−, U2+,U2−, respectively; the V-phase is connected to V1+, V1−, V2+, V2−,respectively; and W-phase is connected to W1+, W1−, W2+, W2−,respectively.

The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

The rotor core 32 is formed with the permanent magnet inserting holes 34and a hole for passing the shaft 38 therethrough, both formed by punchpress. Thus, the rotor 30 is composed of the rotor core 32 made oflaminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

The rotor core 32 may be divided in the radial direction into an inneryoke area 32A and an outer peripheral area 32B. The outer peripheralarea 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux Bφ from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to form amagnetic circuit.

The permanent magnets 36 can be accommodated in the permanent magnetinserting holes 34 which are bordered by the auxiliary magnetic polearea 32B1 in the circumferential direction and bordered by the magneticpole piece area 32B2 around the outer periphery, thus providing arotating electric machine suitable for high speed rotation.

Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

It is assumed in the example illustrated in FIG. 6 that the rotatingelectric machine is a three-phase motor which comprises the permanentmagnet rotor 36 with the number of poles P being ten, and the statorwith the number of magnetic poles being nine. When the number of statorsalient poles is represented by M and the number of the poles of therotor magnets by P, a structure satisfying the following relationship:

M:P=3n:3n±1 (where n is a positive integer) can realize reduced torquepulsations and an increased utilization ratio of windings (windingcoefficient), so that a highly efficient, a small and light-weightrotating electric machine can be provided.

The connection of the stator windings 24 is made in accordance with athree-phase stator winding scheme. More specifically, U1+, U1−, U2+ areconnected in the illustrated order in the U-phase; V1+, V1−, V2+ areconnected in the illustrated order in the V-phase; and W1+, W1−, W2+ areconnected in the illustrated order in the W-phase. Here, the windingsconstituting the respective phases, for example, U1+ and U1−, and U1−and U2+ in the U-phase; V1+ and V1−, V1− and V2+ in the V-phase; and W1+and W1−, W1− and W2+ in the W-phase, have a phase difference of 20degrees in electrical angle. In this way, the stator salient poleshaving wound therearound the stator windings connected to the samephase, increase at least one stator salient pole which has a differentphase with respect to the associated permanent magnet. Take, as anexample, a stator salient pole having wound therearound the winding U1−and a stator salient pole having wound therearound the winding U2+.Assuming that U1− is in phase with the permanent magnet 36A, U1− isshifted from the permanent magnet 36B by an angular distance of 30degrees. This contributes to a reduction in pulsating torque which maycause a problem in the concentrated winding stator.

An electrical angle between adjacent stator salient poles 22B iscalculated to be 200 degrees (180×(10/9)=200), and 20 degrees whentaking into account the phase difference. The cogging torque of thepermanent magnet rotating electric machine exhibits a number ofpulsations per rotation equal to the least common multiple of the numberof permanent magnets and the number of stator salient poles, i.e., 90per rotation in this example.

In the example illustrated in FIG. 2 in which the ratio of the number ofpermanent magnets M to the number of stator salient poles P is 10:12,the cogging torque of the permanent magnet rotating electric machineexhibits pulsations of 60 per rotation. It is understood from thisdiscussion that the second embodiment can further reduce the coggingtorque.

It goes without saying that while the foregoing description has beenmade in connection with an example of a motor, the second embodiment canbe similarly applied to a generator.

According to the second embodiment, since a concentrated winding statoris employed, the end coil portions of the stator can be reduced inlength, so that a smaller rotating electric machine can be provided.

Also, since the stator salient poles, having wound therearound statorwindings connected to the same phase, include at least one salient polewhich has a different phase with respect to the associated permanentmagnet, this configuration reduces the pulsating torque which may causea problem in the concentrated winding stator.

In addition, the cogging torque can be further reduced.

Further, since the permanent magnet rotor is provided with auxiliarymagnetic poles, a structure suitable for field weakening control isrealized, thereby providing a rotating electric machine appropriate tohigh speed rotations.

Furthermore, since an auxiliary magnetic pole area made of a magneticmaterial having a higher magnetic permeability than the permanentmagnets is positioned between the permanent magnets, increased torquecan be generated.

Moreover, the permanent magnets are surrounded by silicon steel plates,so that a rotating electric machine suitable for high speed rotationscan be provided.

Next, a permanent magnet rotating electric machine according to a thirdembodiment of the present invention will be described with reference toFIG. 7.

FIG. 7 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to the third embodiment of thepresent invention.

The third embodiment is characterized by a three-phase motor structurewhich comprises a permanent magnet rotor 36 having twelve poles (P=12)and a stator having eight magnetic poles (M=8). Since this structure canincrease the utilization ratio of windings (winding coefficient), ahighly efficient, small, and light-weight rotating electric machine canbe provided.

Referring specifically to FIG. 7, the rotating electric machine 10comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, end coilportions can be reduced in length, and consequently the physical size ofthe rotating electric machine can also be reduced.

The U-phase of the stator windings 24 is connected to U1, U2, U3, U4,respectively; the V-phase is connected to V1, V2, V3, V4, respectively;and W-phase is connected to W1, W2, W3, W4, respectively.

The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

The rotor core 32 is formed with the permanent magnet inserting holes 34and a hole for passing the shaft 38 therethrough, both formed by punchpress. Thus, the rotor 30 is composed of the rotor core 32 made oflaminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

The rotor core 32 may be divided in the radial direction into an inneryoke area 32A and an outer peripheral area 32B. The outer peripheralarea 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux Bφ from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to form amagnetic circuit.

The permanent magnets 36 can be accommodated in the permanent magnetinserting holes 34 which are bordered by the auxiliary magnetic polearea 32B1 in the circumferential direction and bordered by the magneticpole piece area 32B2 around the outer periphery, thus providing arotating electric machine suitable for high speed rotation.

Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

It is assumed in the example illustrated in FIG. 7 that the rotatingelectric machine is a three-phase motor which comprises the permanentmagnet rotor 36 with the number of poles P being twelve, and the statorwith the number of magnetic poles being eight. Since such a structureachieves an increased utilization ratio of the windings (windingcoefficient), a highly efficient, small and light-weight rotatingelectric machine can be provided.

The connection of the stator windings 24 is made in accordance with athree-phase stator winding scheme. More specifically, U1, U2, U3, U4 areconnected in the illustrated order in the U-phase; V1, V2, V3, V4 areconnected in the illustrated order in the V-phase; and W1, W2, W3, W4are connected in the illustrated order in the W-phase. The windingsforming parts of the U-phase, V-phase, W-phase have a phase differenceof 60 degrees between each other.

In the third embodiment, the stator salient poles having woundtherearound the stator windings connected to the same phase are in phasewith the associated permanent magnets, so that a reduction in torquepulsation is not expected. However, since the salient poles in phasewith the permanent magnets are positioned in a symmetric configuration,a well balanced structure can be provided. More specifically explainingwith reference to the U-phase, the respective salient poles U1, U2, U3,U4 are positioned symmetrically about the shaft 38.

It goes without saying that while the foregoing description has beenmade in connection with an example of a motor, the third embodiment canbe similarly applied to a generator.

According to the third embodiment, since a concentrated winding statoris employed, the end coil portions of the stator can be reduced inlength, so that a smaller rotating electric machine can be provided.

Also, since the permanent magnet rotor is provided with auxiliarymagnetic poles, a structure suitable for field weakening control isrealized, thereby providing a rotating electric machine appropriate tohigh speed rotations.

Further, since an auxiliary magnetic pole area made of a magneticmaterial having a higher magnetic permeability than the permanentmagnets is positioned between the permanent magnets, increased torquecan be generated.

Moreover, the permanent magnets are surrounded by silicon steel plates,so that a rotating electric machine suitable for high speed rotationscan be provided.

Next, a permanent magnet rotating electric machine according to a fourthembodiment of the present invention will be described with reference toFIG. 8.

FIG. 8 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to the fourth embodiment of thepresent invention.

The fourth embodiment is characterized by a three-phase motor structurewhich comprises a permanent magnet rotor 36 having twelve poles (P=12)and a stator having eight magnetic poles (M=8). Since this structure canincrease the utilization ratio of windings (winding coefficient), ahighly efficient, small, and light-weight rotating electric machine canbe provided.

In addition, a magnetic pole piece area of the rotor is projected towardthe magnetic poles of the stator, such that a sinusoidal magnetic fluxdistribution is produced.

Referring specifically to FIG. 8, the rotating electric machine 10comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, end coilportions can be reduced in length, and consequently the physical size ofthe rotating electric machine can also be reduced.

The U-phase of the stator windings 24 is connected to U1, U2, U3, U4,respectively; the V-phase is connected to V1, V2, V3, V4, respectively;and W-phase is connected to W1, W2, W3, W4, respectively.

The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

The rotor core 32 is formed with the permanent magnet inserting holes 34and a hole for passing the shaft 38 therethrough, both formed by punchpress. Thus, the rotor 30 is composed of the rotor core 32 made oflaminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

The rotor core 32 may be divided in the radial direction into an inneryoke area 32A and an outer peripheral area 32B. The outer peripheralarea 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. In the fourth embodiment,the magnetic pole piece area of the rotor is projected toward the statormagnetic poles 22B to shape a sinusoidal magnetic flux distribution.

The permanent magnets 36 can be accommodated in the permanent magnetinserting holes 34 which are bordered by the auxiliary magnetic polearea 32B1 in the circumferential direction and bordered by the magneticpole piece area 32B2 around the outer periphery, thus providing arotating electric machine suitable for high speed rotation.

Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

It is assumed in the example illustrated in FIG. 8 that the rotatingelectric machine is a three-phase motor which comprises the permanentmagnet rotor 36 with the number of poles P being twelve, and the statorwith the number of magnetic poles being eight. Since such a structureachieves an increased utilization ratio of the windings (windingcoefficient), a highly efficient, small and light-weight rotatingelectric machine can be provided.

The connection of the stator windings 24 is made in accordance with athree-phase stator winding scheme. More specifically, U1, U2, U3, U4 areconnected in the illustrated order in the U-phase; V1, V2, V3, V4 areconnected in the illustrated order in the V-phase; and W1, W2, W3, W4are connected in the illustrated order in the W-phase. The windingsforming parts of the U-phase, V-phase, W-phase have a phase differenceof 60 degrees between each other.

In the fourth embodiment, the stator salient poles, having woundtherearound the stator windings connected to the same phase, are inphase with the associated permanent magnets, so that a reduction intorque pulsation is not expected. However, since the salient poles inphase with the permanent magnets are positioned in a symmetricconfiguration, a well balanced structure can be provided. Morespecifically explaining with reference to the U-phase, the respectivesalient poles U1, U2, U3, U4 are positioned symmetrically about theshaft 38.

It goes without saying that while the foregoing description has beenmade in connection with an example of a motor, the fourth embodiment canbe similarly applied to a generator.

According to the fourth embodiment, since a concentrated winding statoris employed, the end coil portions of the stator can be reduced inlength, so that a smaller rotating electric machine can be provided.

Also, since the permanent magnet rotor is employed, a structure suitablefor field weakening control is realized, thereby providing a rotatingelectric machine appropriate to high speed rotations.

Moreover, the permanent magnets are surrounded by silicon steel plates,so that a rotating electric machine suitable for high speed rotationscan be provided.

While the foregoing respective embodiments have been described inconnection with a control system which controls a sinusoidal currentwith respect to the position of the rotor, it goes without saying thatthe present invention may also be applied to a 120 degree conductivebrash-less motor scheme which does not perform a current control.

Also, while the foregoing description has been made with reference to aninternal rotation type motor, the present invention may also be appliedto external rotation type motors, generators, and linear motors.

Next, an electric car employing a permanent magnet rotating electricmachine according to a fifth embodiment will be described with referenceto FIG. 9.

FIG. 9 is a block diagram illustrating the configuration of an electriccar which is equipped with a permanent magnet rotating electric machineaccording to the fifth embodiment of the present invention.

A body 100 of the electric car is supported by four wheels 110, 112,114, 116. Since this electric car is a front-wheel driven type, apermanent magnet rotating electric machine 120 is directly coupled to afront wheel shaft 154. The permanent magnet rotating electric machine120 has a structure as illustrated in FIG. 2, 6, 7 or 8. A control unit130 is provided for controlling driving torque of the permanent magnetrotating electric machine 120. A battery 140 is provided as a powersource for the control unit 130. Electric power from the battery 140 issupplied to the permanent magnet rotating electric machine 120 throughthe control unit 130, thereby driving the permanent magnet rotatingelectric machine 120 to rotate the wheels 110, 114. The rotation of asteering wheel 150 is transmitted to the two wheels 110, 114 through atransmission mechanism including a steering ring gear 152, a tie rod, aknuckle arm, and so on to change the angle of the wheels 110, 114.

It should be noted that while in the foregoing embodiment, the permanentmagnet rotating electric machine has been described to be used fordriving wheels of an electric car, the permanent magnet rotatingelectric machine may also be used for driving wheels of an electriclocomotive or the like.

According to the fifth embodiment, when the permanent magnet rotatingelectric machine is applied to an electrically driven vehicle,particular to an electric car, a small, light-weight, and highlyefficient permanent magnet rotating electric machine can be equipped inthe vehicle, thus making it possible to provide an electric car whichcan run a longer distance with the amount of electric power accumulatedin one recharging operation.

1. A driving apparatus for a vehicle, comprising a rotating electricmachine, wherein: said rotating electric machine has a stator and arotor held rotatably inside said stator; said stator comprises a statorcore and stator windings; said stator windings comprise three-phasewindings which are wound on said stator core; said rotor comprises arotor core and a plurality of permanent magnets held inside said rotorcore; a plurality of auxiliary magnetic pole areas are formed in saidrotor core, along a radial direction of said rotor core; said permanentmagnets are arranged between said auxiliary magnetic pole areas, so thatpermanent magnets which are located both sides of said each of saidauxiliary magnetic pole areas have different polarities; a reluctancetorque is generated at said auxiliary magnetic pole areas based on amagnetomotive force which is generated by three phase current flowingthrough said stator windings; said driving apparatus further comprisesan inverter; and said three-phase current flowing through said statorwindings are controlled by said inverter.
 2. A driving apparatus for avehicle, comprising a rotating electric machine, wherein: said rotatingelectric machine has a stator and a rotor held rotatably inside saidstator; said stator comprises a stator core and stator windings; saidstator windings comprise U-phase, V-phase and W-phase windings; saidrotor comprises a rotor core and a plurality of permanent magnets, aplurality of magnet inserting holes are formed inside said rotor core;said permanent magnets are inserted in said magnet inserting holes; aplurality of auxiliary magnetic pole areas are formed surrounding ofsaid rotor core; said magnet inserting holes are arranged between saidauxiliary magnetic pole areas, with permanent magnets which are locatedboth sides of said each of said auxiliary magnetic pole areas havingdifferent polarities; a reluctance torque is generated at said auxiliarymagnetic pole areas based on a magnetomotive force which is generated bythree phase current flowing through said stator windings of saidU-phase, V-phase and W-phase; said driving apparatus further comprisesan inverter; and said three-phase current flowing through said statorwindings is supplied by said inverter.
 3. A driving apparatus for avehicle, comprising a rotating electric machine, wherein: said rotatingelectric machine has a stator and a rotor held rotatably inside saidstator; said stator comprises a stator core and stator windings woundaround said stator core; said stator windings comprise U-phase, V-phaseand W-phase windings; said rotor comprising a rotor core and a pluralityof permanent magnets held in said rotor core; a plurality of auxiliarymagnetic pole areas are formed in said rotor core, along a radialdirection of said rotor core; magnet inserting holes are arranged insaid rotor core, between said auxiliary magnetic pole areas; saidpermanent magnets are inserted in said magnet inserting holes so that apermanent magnet which is located on one side of said auxiliary magneticpole areas and another permanent magnet which is located on another sideof said auxiliary magnetic pole areas have different polarities; saidrotor has a number of poles that is different from a number of poles ofsaid stator; said auxiliary magnetic pole areas generate a reluctancetorque based on a magnetomotive force which is generated by saidU-phase, V-phase and W-phase windings of said stator; said drivingapparatus further comprises an inverter; and said three-phase current isflowed through said stator windings by said inverter.
 4. A drivingapparatus for a vehicle, comprising a rotating electric machine,wherein: said rotating electric machine has a stator and a rotor heldrotatably inside said stator; said stator comprises a stator core andstator windings wound around said stator core; said stator windingscomprise U-phase, V-phase and W-phase windings; said rotor comprises arotor core and a plurality of permanent magnets held inside said rotorcore; a plurality of auxiliary magnetic pole areas are formed in saidrotor core, along a radial direction of said rotor core; magnetinserting holes are arranged in said rotor core, between said auxiliarymagnetic pole areas; said permanent magnets are arranged in said magnetinserting holes so that polarities of permanent magnets which arelocated both sides of said auxiliary magnetic pole areas are different;a number of poles of said rotor is multiple of three, and differs from anumber of poles of said stator; said driving apparatus further comprisesan inverter; and said three-phase current flowing through said statorwindings is supplied by said inverter.
 5. A driving apparatus for avehicle, comprising a rotating electric machine, wherein: said rotatingelectric machine has a stator and a rotor held rotatably inside saidstator; said stator comprises a stator core and stator windings woundaround said stator core; said rotor comprises a rotor core and aplurality of permanent magnets held inside said rotor core; a pluralityof auxiliary magnetic pole areas are formed along the radial directionof said rotor core and in said rotor core; magnet inserting holes arearranged in said rotor core, between said auxiliary magnetic pole areas;said permanent magnets are arranged in said magnet inserting holes so asthat polarities of permanent magnets which are located both sides ofsaid auxiliary magnetic pole areas are different; a number of poles ofsaid rotor is multiple of three; said stator windings comprise U-phase,V-phase and W-phase windings; a three phase alternating current issupplied to said stator windings; a reluctance torque is generated atsaid auxiliary magnetic pole areas; the number of poles of said rotor isdifferent from a number of poles of said stator; said driving apparatusfurther comprises an inverter; and said three-phase current flowingthrough said stator windings is supplied by said inverter.
 6. A drivingapparatus for a vehicle, comprising a rotating electric machine,wherein: said rotating electric machine has a stator and a rotor heldrotatably inside said stator; said stator comprises a stator core andstator windings wound around said stator core; said rotor comprises arotor core and a plurality of permanent magnets held inside said rotorcore; a plurality of auxiliary magnetic pole areas are formed in saidrotor core, along a radial direction of said rotor core; magnetinserting holes are arranged in said rotor core, between said auxiliarymagnetic pole areas; said permanent magnets are arranged in said magnetinserting holes so as that polarities of permanent magnets which arelocated both sides of said auxiliary magnetic pole areas are different;a number of poles of said rotor is multiple of three; said statorwindings comprise U-phase, V-phase and W-phase windings; said U-phase,V-phase and W-phase windings are connected as a star connection; threephase alternative current is supplied to said stator windings; areluctance torque is generated at said auxiliary magnetic pole areas;the number of poles of said rotor is different from a number of poles ofsaid stator; said driving apparatus further comprises an inverter; andsaid three-phase current is flowed through said stator windings by saidinverter.
 7. A driving apparatus according to claim 1, wherein: magneticpole piece areas are formed at said stator core and at outer side ofsaid permanent magnets; and magnetic circuits are formed which leadmagnetic flux to a stator side through said permanent magnets and saidmagnetic pole piece areas.
 8. A driving apparatus according to claim 7,wherein a number of poles of said rotor is eight.
 9. A driving apparatusaccording to claim 8, wherein a number of poles of said rotor is ten.